If you want to ensure you have adequate passwords but don't have the time or interest to study the topic, there's a useful basic article on how to devise strong passwords over at the NY Times. It summarizes key points in 9 simple rules of thumb. Also see the follow-up article for useful reader feedback. Stay safe!

I'm ignorant on these matters, but I don't see how passphrases could feasibly be cracked using dictionary based attacks.

The number of possible words and alternate "spellings" is large, especially if you consider multiple languages as you've mentioned.

While you're right that such attacks would require massive dictionary of words - it's still significantly more streamlined than a typical 'brute force attack' which will try every character combination individually.

You also mentioned "without writing it down", but I was under the impression that was also out of date ideas about password protection. The chances of someone physically getting your password is practically zero, since most people won't risk it, most people aren't that important, and those who do risk stealing things generally aren't after written down passwords (assuming they know the username the person uses).

You're talking about 'security through obscurity' and that's a pretty bad philosophy to have.

There's been cases where 'normal' individuals like ourselves have become over-night public figures because of stories that break out in the press (eg relatives of crime suspects) and have subsequently been stalked over social media by reporters after a cheap story.

There's also cases about answer phone hacking that broke out earlier this year and many of those cases were against regular people.

And finally, regular people do get their accounts hacked all the time (eg my Paypal account was hacked a few years ago)